Safety guard arrangement for circular saw

ABSTRACT

A safety guard arrangement for a motor-driven circular saw utilizes a weight biased guard and a solenoid actuated linkage for moving the guard. The weight normally biases the guard into either a guarding position or a storage position and the guard is moved from one position to another by pulsing of the solenoid. Pulsing of the solenoid is controlled by a switch related to a switch for control of the main motor so that the solenoid is pulsed and the guard moved to the storage position when the motor is started and the solenoid is pulsed and the guard moved back in guarding position when the motor is stopped.

United States Patent Dolen A. De Pue 5109 26th Ave., Washington, D.C. 200.31 857,079

Sept. 11, 1969 Oct. 19, I97 1 Inventor Appl. No. Filed Patented SAFETY GUARD ARRANGEMENT FOR CIRCULAR SAW 43,159 H, 159; l44/25l References Cited Primary ExaminerDonald R. Schran Attorney- Sughrue, Rothwell, Mion, Zinn & Mac Peak ABSTRACT: A safety guard arrangement for a motor-driven circular saw utilizes a weight biased guard and a solenoid actuated linkage for moving the guard. The weight normally biases the guard into either a guarding position or a storage position and the guard is moved from one position to another by pulsing of the solenoid. Pulsing of the solenoid is controlled by a switch related to a switch for control of the main motor so that the solenoid is pulsed and the guard moved to the storage position when the motor is started and the solenoid is pulsed and the guard moved back in guarding position when the motor is stopped PATENTEBDBT 19 197i SHEET 1 UF 2 FIG. 3

INVENTOR DOLEN A. DEPUE PATENTEDUCT 19 l97l 3.613.748

SHEET 2 BF 2 INVE NTOR DOLEN A. DEPUE S m W ATTORNEYS SAFETY GUARD ARRANGEMENT FOR CIRCULAR SAW BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to improvements in safety guards for power saws of the circular saw type and particularly to a unique arrangement for moving the safety guard from its guarding position to its storage position and vice versa.

2. Description of the Prior Art Safety guards for circular saws are well known in the art and perform a valuable function in protecting the user of the saw. These guards are usually of the type having a U-shaped section surrounding the saw blade and are swingably or rotatably mounted so that the U-shaped section covers the saw blade normally but can be swung into an upper housing portion to expose the saw blade during cutting. Normally, a spring biases the saw guard to its guarding position and movement of the saw into lumber to be cut forces the saw guard toward its storage position. However, when cutting certain types of materials, the saw guard will hang up on the material and not readily move against the spring bias to its storage position for cutting. This is vexatious to the user of the saw and it is not uncommon for such users to completely remove the saw guard when cutting certain materials. This in turn leads to a highly unsafe condition of the saw for further use. Furthermore, pushing the guard against the spring bias causes a drag on the saw in operation and this is undesirable.

Various other arrangements have been known in the patented art for positioning a protective guard including the use of a solenoid with a spring biasing the guard to its guarding position and a complex linkage connecting the guard to the solenoid, the solenoid being operated and energized the entire time the saw is energized. (See the US. Pat. to Amoldy, No. 2,722,246, granted Nov. 1, 1955.) Another patentee has approached this problem by incorporating a linear motor in the cell guard. (See the US. Pat. to Winther, No. 3,410,325, granted Nov. 12, 1968.) Both of these approaches have not met with any significant commercial acceptance due to the complexity and consequent additional expense of the construction.

SUMMARY OF THE INVENTION This invention provides a protective or safety guard for a motor powered rotary or circular saw which eliminates the problem of hanging up the guard with the material being cut, is automatic in operation, is much safer than the prior art guards, does not inconvenience the user, and provides no drag on the saw in operation.

The construction which accomplishes these results, includes a movable guard for circular saw, the guard having a weight adjacent one end so as to be normally weight-biased in one of either two extreme positions, a guarding position or a stored position to allow cutting. Movement of the guard from one position to another is accomplished by pulsing a solenoid which is connected to the guard by a linkage. On pulsing the solenoid, the linkage quickly pulls the guard and the momenturn of the weight causes the guard to move from one of the extreme positions to the other and the weight then holds the guard in the position to which it is moved. Pulsing of the solenoid is accomplished by a switch which is physically related to the motor switch so that on pulling a trigger to operate the motor switch, the solenoid is pulsed and the guard is removed from its guarding position to its storage position just prior to the motor being actuated. While the saw motor is operating normally, the solenoid is not actuated but the weight holds the guard in its storage position. n releasing the trigger to shut off the motor, the solenoid switch is actuated again, again pulsing the solenoid and moving the guard from its storage position back to its guarding position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front elevational view of a circular saw having the protective safety guard of this invention;

2 is a front elevational view with the housing shown in section and portions removed for the sake of clarity illustrating the operation of the guard and its solenoid actuator and showing the guard in its guarding position;

FIG. 3 is a sectional elevational view similar to FIG. 2 showing the guard in its storage position to allow cutting;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is a detail elevational view of the trigger assembly showing switches controlling operation of the circular saw motor and the guard moving solenoid;

FIG. 6 is an electrical circuit diagram with mechanical components shown schematically illustrating the operation of the switches controlling the guard-actuating solenoid and the motor;

FIG. 7 is the circuit diagram of FIG. 6 with the mechanical components shown in the position with the saw motor actuated and after the guard solenoid has been pulsed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A rotary or-circular saw 10 of the motor driven portable type is shown in FIG. 1. The saw construction includes a frame 12 which carries an electric motor 14, FIG. 4, for driving a circular saw blade 16 in a rotary manner, the saw blade being secured to motor shaft 18. The operation of the motor 14 and hence the saw blade 16 is controlled by a motor control switch assembly 20.

The frame 12 includes a saw blade housing portion 22 which is generally U-shaped in section and covers the upper portion of the circular saw blade 16. A saw blade guard 24 is journaled by its circular flange 25 on motor shaft 18, FIG. 4, so as to be swingable from a guarding position as shown in FIG. 2 to a storage position as shown in FIG. 3 to allow cutting. As shown in FIG. 4, the guard is U-shaped in section along its outer periphery to enclose the teeth of the saw 16 as is well known in the art. As shown in FIG. I, the saw may include other guards and guides 26 as is conventional.

The saw blade protector or guard 24 of this invention has biasing means in the form of a weight 28 integral with the guard adjacent one end thereof. This weight will always tend to assume the lowest position when the saw is held with the saw blade vertical as shown in FIG. 1 and with appropriate stop means will cause the blade to stay in one of the two extreme positions illustrated in FIGS. 2 and 3.

For operating the guard to move it from one position to another, a solenoid 30 is provided. This solenoid is mounted in a mounting boss 32 in the frame 12 and is connected to the saw guard 24 by a linkage including link 34. Link 34 has one end connected to the solenoid plunger 36 and the other end connected at rotary connection 38 to the saw guard 24. The extreme limits of the solenoid plunger determine and provide stops for the saw guard 26 in the position shown in FIGS. 2 and 3.

For operating the saw and pulsing the solenoid, there is provided a trigger 40 in the motor control switch assembly 20. This trigger is of the usual type pivotally mounted so that, upon actuation, it slides a trigger bar 42. The trigger bar 42 carries actuating earns 44 and 46 which actuate microswitches 48 and 50, respectively controlling the solenoid 30 and saw motor 14. The earns 44 and 46 and the switches 48 and 50 are positioned such that on squeezing of the trigger 40 and shifting the bar 42 to the right as shown in FIGS. 6 and 7, switch 48 will be operated momentarily pulsing solenoid 30, then switch 50 will be closed starting motor 14 and switch 48 will be open. On releasing the trigger, the opposite occurs; the switch 50 will be open, the switch 48 will be closed so that the motor will turn off and the solenoid will be pulsed to return the guard to guarding position.

The operation is believed to be apparent from the foregoing but a brief resume will now be given. When electric cord plug 52 is plugged into a source of electric current, before power is applied the weight 28 will cause the guard 24 to assume its guarding position. In operation, the user would first pull the trigger 40 of the switch assembly 20. Cam 44 would close switch 48 pulsing solenoid 30 causing the link 34 to quickly pull on the saw guard 24 moving it in a clockwise manner from the position of FIG. 2 to the position of FIG. 3. The momentum of weight 28 assists in this movement due to the quick pulsing actuation of the solenoid. The weight 28 then assists in holding the saw guard 24 in the position of FIG. 3 which is the storage position to allow cutting by the saw blade 16. Continued squeezing of the trigger switch in order to start the saw motor 14 releases the solenoid 30 and cam 46 closes switch 50 starting motor 14 and driving the saw blade 16, see FIG. 7 The saw is then used normally as any circular saw would be used. At the time the trigger 40 is released to stop the saw motor, the trigger bar 42 moves to the right from the position shown in FIG. 7 to the position shown in FIG. 6, and in the course of so moving, switch 50 opens stopping motor 14 and cam 44 then momentarily closes switch 48 pulsing solenoid 30. This pulsing causes link 34 to pull on the guard 24 from its position in FIG. 3, the momentum of weight 28 causes the guard to continue its movement until it assumes the position of FIG. 2 which is the protective guarding position.

It can be seen that applicant has provided a unique and quite simple arrangement for automating the actuation of a circular saw guard of as to prevent hangup, inconvenience, and eliminate drag on the saw guard. The resulting construction is much safer and much more convenient to the user.

What is claimed is:

l. A rotary saw of the type including a frame, an electric motor carried by the frame, a circular saw blade journaled on the frame and driven by the motor, a motor control electric switch on the frame controlling electric power to the motor, a saw blade housing portion of the frame enclosing an upper portion of the saw blade, and a saw blade guard journaled on the same axis as the saw blade and movable to enclose the saw blade or expose the saw blade to allow cutting, the movement of the saw blade guard being from a guarding position covering a lower portion of the saw blade to a storage position within the saw blade housing portion of the frame, improvements in means for moving the saw blade guard from the guarding position to the storage position and vice versa, comprising;

a weight on the saw guard normally biasing the saw guard to hold it in either the guarding or storage position,

a solenoid carried by the frame,

a linkage connecting the solenoid with the saw guard so that when the solenoid is actuated the linkage overcomes the biasing means and moves the saw guard from one position to the other and the biasing means then holds the saw guard in the other position,

a solenoid control electric switch controlling electric power to pulse the solenoid, the solenoid control switch related to the motor-controlled switch such that on closing the motor control switch, the solenoid control switch is closed to pulse the solenoid and on opening the motor control switch, the solenoid controlled switch is opened to pulse the solenoid.

2. A rotary saw of the type including a frame, an electric motor carried by the frame, a circular saw blade journaled on the frame and driven by the motor, a motor control electric switch on the frame-controlling electric power to the motor, a saw blade housing portion of the frame enclosing an upper portion of the saw blade, and a saw blade guard journaled on the same axis as the saw blade and movable to enclose the saw blade or expose the saw blade to allow cutting, the movement of the saw blade guard being from a guarding position covering a lower portion of the saw blade to a storage position within the saw blade housing portion of the frame, improve ments in means for moving the saw blade guard from the guarding position to the storage position and vice versa, comprising;

means normally biasing the saw guard to hold it in either the guarding or storage position,

a solenoid carried by the frame,

a linkage connecting the solenoid with the saw guard so that when the solenoid is actuated the linkage overcomes the biasing means and moves the saw guard from one position to the other and the biasing means then holds the saw guard in the other position,

a solenoid control electric switch controlling electric power to pulse the solenoid, the solenoid control switch related to the motor controlled switch such that on closing the motor control switch, the solenoid control switch is closed to pulse the solenoid and on opening the motor control switch, the solenoid-controlled switch is opened to pulse the solenoid, and a trigger-type switch actuator for actuating the motor control switch and solenoid control switch, the motor control switch being actuated after the solenoid control switch when the trigger is squeezed and the solenoid control switch being actuated after the motor control switch when the trigger is released. 

1. A rotary saw of the type including a frame, an electric motor carried by the frame, a circular saw blade journaled on the frame and driven by the motor, a motor control electric switch on the frame controlling electric power to the motor, a saw blade housing portion of the frame enclosing an upper portion of the saw blade, and a saw blade guard journaled on the same axis as the saw blade and movable to enclose the saw blade or expose the saw blade to allow cutting, the movement of the saw blade guard being from a guarding position covering a lower portion of the saw blade to a storage position within the saw blade housing portion of the frame, improvements in means for moving the saw blade guard from the guarding position to the storage position and vice versa, comprising; a weight on the saw guard normally biasing the saw guard to hold it in either the guarding or storage position, a solenoid carried by the frame, a linkage connecting the solenoid with the saw guard so that when the solenoid is actuated the linkage overcomes the biasing means and moves the saw guard from one position to the other and the biasing means then holds the saw guard in the other position, a solenoid control electric switch controlling electric power To pulse the solenoid, the solenoid control switch related to the motor-controlled switch such that on closing the motor control switch, the solenoid control switch is closed to pulse the solenoid and on opening the motor control switch, the solenoid controlled switch is opened to pulse the solenoid.
 2. A rotary saw of the type including a frame, an electric motor carried by the frame, a circular saw blade journaled on the frame and driven by the motor, a motor control electric switch on the frame-controlling electric power to the motor, a saw blade housing portion of the frame enclosing an upper portion of the saw blade, and a saw blade guard journaled on the same axis as the saw blade and movable to enclose the saw blade or expose the saw blade to allow cutting, the movement of the saw blade guard being from a guarding position covering a lower portion of the saw blade to a storage position within the saw blade housing portion of the frame, improvements in means for moving the saw blade guard from the guarding position to the storage position and vice versa, comprising; means normally biasing the saw guard to hold it in either the guarding or storage position, a solenoid carried by the frame, a linkage connecting the solenoid with the saw guard so that when the solenoid is actuated the linkage overcomes the biasing means and moves the saw guard from one position to the other and the biasing means then holds the saw guard in the other position, a solenoid control electric switch controlling electric power to pulse the solenoid, the solenoid control switch related to the motor controlled switch such that on closing the motor control switch, the solenoid control switch is closed to pulse the solenoid and on opening the motor control switch, the solenoid-controlled switch is opened to pulse the solenoid, and a trigger-type switch actuator for actuating the motor control switch and solenoid control switch, the motor control switch being actuated after the solenoid control switch when the trigger is squeezed and the solenoid control switch being actuated after the motor control switch when the trigger is released. 